Vacuum switch



Dec. 19, 1961 J. D. COBINE ETAL VACUUM SWITCH Filed Jan. 2, 1959 Fig. 2.

United States Patent Ofihee 3,014,107 Patented Dec. 19, 1961 3,014,107 VACUUM SWITCH James D. Cobine, Rexford, and Emmett E. Burger, Schenectady, N.Y., assiguors to General Electric Company, a corporation of New York Filed Jan. 2, 1959, Ser. No. 784,726 4' Claims. (Cl. 200 144) The present invention relates to an improved vacuum type switch for alternating current circuits in which an arc is formed on circuit opening and sustained until substantially current zero is reached. The present invention isparticula'rly directed to a switch of this type using an electrode material having a relatively high vapor pressure in conjunction with a unique mechanical construction that maintains rapid arc motion over the electrodes until the current zero is substantially reached.

Invacuum type switches current'flow between the electrodes is maintained by the ionized vapor formed by the electrode material itself. Such vapor is formed by the heat andother effects of the are at the points of contact between the arc and the electrode-faces. If the switch is to carry an alternating current until substantially the zero current condition, it is necessary to utilize an electrode material that vaporizes without undue difiiculty. Such electrode materials, however, are readily eroded by the arc and thus tend to deteriorate rapidly in actual commercial switching applications.

The vacuum switch of the present invention is defined by an insulating envelope Within which a pair of relatively movable electrodes are-located. At least the arcing surfaces of these electrodes are of readily vaporized material. Removed from the arcingsurfaces, the electrodes define oppositely wound facing solenoids, within which are preferably placed magnetic cores serving to concentrate and maximize the radial fringing flux in the space between the arcing surfaces. This radial fringing flux imparts a rotational movement to the are, causing it to travel over a large electrode area and preventing undue localized electrode erosion. Further in accordance with the present invention, the contours of the arcing surfaces of the electrodes are made to substantially follow the direction of the magnetic field, thereby orienting the arc in transverse relation to the magnetic field and assuring maximum motion of the footpoints of the arc and minimizing'the tendency of the are to dwell in any single region of an electrode.

It is therefore a general object of the present invention to provide an improved vacuum switch for alternating current'circuits in which a readily vaporized electrode material is used in conjunctionwith magnetic action to provide ample ionized metal vapor to sustain the arc until substantially current zero, while at the same time distributing the electrode erosion over a large area of each electrode.

A more particular object of the present invent-ion is to provide apparatus ofithe foregoing type in which the electrodes themselves provide the necessary magnetic fifild.

Still another object of the present invention is to provide an improved vacuum switch combining a pair of contact members, each including means for establishing and maintaining a circuit interrupting arc and self induced magnetic means for keeping the arc in motion until extinction.

Our invention further resides in a..switch.of the foregoingtype having features of construction,combination and arrangement making it simple in construction, reliable in operation, readily manufactured and operated and in other respects serving to provide a device having maximum commercial usefulness.

The novel features which we believe to be characteristiee of our invention are set forth with particularity in the appended claims. Our invention itself, however, together with further objects and advantages-thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is an axial cross-sectional view with parts in elevation of a complete switch constructed in accordance with the present invention;

FIG. 2 is a greatly enlarged fragmentary'view in elevation of the electrodes of the switch of FIG. 1, showing the same in the contacting circuit-opening position;

FIG. 3 is a fragmentary view'ofa modified form of the switch of FIGS. 1 and 2; and

FIG. 4 is a cross-sectional view along axis 4-4, FIG. 3.

As shown in FIG. 1, a switch constructed in accord with our inventin may comprise an envelop 10 of glass or other suitable vacuum-tight insulating material. This envelop defines the vacuum space 12. At end 10a, the envelop 10 embeds the stem 14a of the fixed electrode 14, described in further detail hereafter. At its opposite end 1017 the envelop embeds the flange 16a of the vacuum tight bellows 16. These bellows receive and movably support the stem 18a of the movable electrodes 18, described in further detail hereafter. The stem 18a is attached to suitable operating mechanism (not shown) to move the electrode 18 in the axial direction between the spaced closed circuit position in relation to electrode 14 as shown in FIG. 1 and the open-circuit position shown in FIG. 2. Envelop 10 is evacuated and maintained-at a pressure of at least as low as 10- mm. of mercury in order that no ionizable gases be present to impede vacuum circuit interruption.

The detailed construction of the electrodes 14 and 18 is seen best in FIG. 2. As shown, the electrode 14 has a head end 14b in the form of a solid of revolution about the axis of the electrodes and defining the annular flat contacting face 140. Opposite the face 140, the head receives the helical solenoid-defining conductor 14d which spirals as shown to be received on the flanged disk-shaped end 142 of the stem 14a as shown in the broken away portion of FIG. 2. These parts may be secured together by welding, brazing or other suitable means.

The cylindrical magnetic core 14]" is disposed within the solenoid 140., as shown. It is affixed at one end to the flanged end 142 of the stem 14 a preferably by suitable means to provide mechanical support and electrical insulation. This core is of anysuitable material having a high magnetic permeability, such as soft iron, silicon steel, etc. As shown in FIG. 2, the core extends the full length of the solenoid 14d .and'through the circular bore 14g in the head 14b 'to a. point close to the plane defined by the contact-making annular face 140.

As shown, the core 14 is within the confines of the.

solenoid 140. and the head 14b.

The electrode 18 is constructed in fashion similar to electrode 14. Its head portion 18b.is likewise a-solid of revolution about the axis of the electrodes defining a flat annular face 18c of the electrode 18. A conductor 13d in the form of a solenoid is afiixed 'to the face of head 18b opposite the annular face and spirals as It will be-noted that thisconductorshown in FIG. 2. spirals in opposite sense to the spiral of the conductor 140.. At its end opposite head 18b, the solenoid conductor 18d is received over the flanged end 18a of the stern 18a. The magnet core 18 FIG. 2, is disposed within the solenoid conductor 18dand is insulatingly afiixed to the flanged end 18:: of the stern 18a. This core extends through the bore 18g of thehead 18b in fashion similar to the core'14f to terminate near theplane of face 18c, and within the confines'of head 18]).

'3 n) The parts of electrode 18 are secured to each other by suitable means. The core 18] is of suitable high permeability material to that of the core 14).

The head portions 14b and 18b of the electrodes, or at least facing surfaces thereof, are made of materials chosen in accordance with the invention set forth in Lee and Cobine patent application S.N. 750,784, filed July 24, 1958, and assigned to the same assignee as the present invention. Such materials are characterized by the ability to vaporize relatively easily under the action of the arc and by other characteristics more particularly set forth in that application. Examples of such materials include tin, antimony, lead, zinc, manganese, bismuth, and suitable alloys thereof. These electrodes may also be made of a moderate vapor pressure material, such as copper or silver, as well. The other current-conducting portions of the electrodes are made of any suitable conducting materials having the required mechanical strength and current-carrying capacity. The vapor supplying materials are suitably refined in vacuo as set forth in the Lee and Cobine application to preclude the release of ionizable gases during operation.

As above noted, the solenoids defined by the conductors 14a and 18d are wound or spiral in opposite senses. Consequently, when a current fiows between the electrodes (either by reason of their contacting relation as in FIG. 1 or by reason of an are between heads 14b and 18b), opposing magnetornotive forces are developed. These forces are directed along the axis of the electrodes since the solenoids spiral about this axis. The resultant magnetic field distribution is determined by the action of the cores 14 and 18 which define relatively low permeability magnetic paths. These paths terminate at the inboard end faces of the cores 18 and 14 where the magnetic fields fringe radially out to turn back about the respective solenoids to the outboard ends of the cores. A representative magnetic flux line about the solenoid 18d is shown at F, FIG. 2. It will be noted that this flux line fringes out in direction substantially parallel to the faces 14c and 18c and then swings back in direction generally parallel to the side face configuration of the head portion 18b of the electrode 18. There are of course many flux lines making up the overall field defined by the solenoid conductors 14d and 18d and the cores 14f and 18 All of these tend to spread radially out near the neutral plane midway between the electrodes and curve back away from the electrodes in manner similar to the flux line 1?, FIG. 2.

The effect of the magnetic flux resulting from the action of the solenoid portions of the electrodes is to rotate the are about the axis of the electrodes. Under normal current conducting conditions, the electrodes are positioned with their faces 14c and 18c in contact-making relation as shown in FIG. 2. When the electrodes are separated as in FIG. 2, an arc is struck between faces 14c and 180 at the moment of interruption (assuming, of course, that electrode opening does not occur at a current zero). Since this arc is generally in the direction of the axis of the electrodes, and since the magnetic field in this region is generally radial, the effect of the action of the arc current and the magnetic field is to cause the arc to rotate about the axis of the electrodes, traversing the facing electrode surfaces at a rapid rate. Normally the arc will tend the climb up on the arcuate faces of the electrodes in response to inherent magnetic blow-out action, but due to the magnetic field distribution associated with the action of the cores and the solenoid portions of the electrodes the rotation about the axis of the electrodes continues. Thus, the are continuously rotates about the surfaces of the electrodes, is continually travelling onto fresh electrode area, and the action of the arc is distributed over a large area of the electrodes.

The contour of the arcing surfaces of head portions 18b and 14b of the respective electrodes is chosen in accordance with the shape of the magnetic fields due to the solenoid portions of these electrodes and the cores 14 and 18]. As shown by the fiux line F, FIG. 2, the contour is such that the arcing surfaces are generally parallel to the flux lines. The are is accordingly substantially normal to the magnetic flux lines at its footpoints of contact with the electrodes so that there is a large component of the current flow at right angles to the magnetic flux. This assures that a maximum interaction takes place between the magnetic field and the are current and that there is no tendency of the arc to approach a point of limited magnetic action and dwell without substantial further movement.

in the embodiment of the invention shown in FIG. 3, a plurality of annular deionizing plates 20 are located in alignment with and external of electrodes 14 and 18. These plates may be of any suitable deionizing material, such as for example, a metal such as copper. These plates also define oool surfaces upon which the evaporated electrode material can condense without impairing the insulating ability of the inside faces of the envelop 10. The plates 20 are held in position by suitable support brackets '22 aflixed to the walls of envelop 10.

In the switch of the present invention, at least the arcing faces of the electrodes 14 and 18 are made of materials that produce relatively copious amounts of vaporized metal. Nevertheless no undue electrode erosion occurs because the arc travels over a large area on each electrode and, in addition, the arc does not at any time tend to dwell at any one position.

it will be noted that the head or arcing portions of, the electrodes, 14b and 18b, define axial cylindrical bores in which the cores 14f and 18 respectively, are located. Since these cores extend almost to the planes of the annular contact-making surfaces and 180, they are particularly effective in creating magnetic field patterns that are essentially radial in the regions of the faces 14c and 180. However, the cores are within the confines of the head portions 141) and 13b. For this reason, coupled with the evacuated character of the space in which the electrodes are located, the arc does not tend to form at or travel to these cores.

While we have shown and described specific forms of the present invention it will of course be understood that many modifications and alternative constructions can be made without departing from its spirit and scope. We, therefore, intend by the appended claims to cover all such modifications and alternative constructions as fall within their true spirit and scope.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An alternating current vacuum switch in which a circuit interrupting arc is maintained by vaporized electrode material until substantially current zero, the switch comprising: means defining a vacuum space having a pressure at least as low as 10 mm. of mercury; a pair of electrodes symmetrical about a common axis and located in said space in opposed relation to define facing arcing surfaces, said electrodes being movable along said axis between a contact-making engaging position and a spaced position establishing a circuit interrupting arc therebetween, each electrode having a head portion and a stem portion, said head portion having an axial bore therein and defining an annular contact face, a solenoid member operatively connecting said head and stem portions, 2. high permeability magnetic core located within the confines of said solenoid member insulatingly connected to said stern portion and extending through the axial bore of said head portion to a position near the plane of said annular contact face, each of said solenoids spiraling in opposite sense to produce substantially identical opposed magnetic fields, said magnetic fields determined by said cores and being substantially parallel with the axis of said electrodes and fringing radially adjacent said annular contact faces, the arcing surfaces of said electrodes having substantially the same shape as the flux lines of said magnetic field, said magnetic field so influencing the circuit interrupting are established through the vaporized metal of the electrodes that said are forms with footpoints substantially normal to said magnetic field rotates about the axis of said electrodes and is maintained on said arcing surfaces until substantially current zero is reached.

2. The vacuum switch of claim 1 wherein the head portion of said electrode has a generally toroidal configuration.

3. An alternating current vacuum switch in which a circuit interrupting arc is maintained by vaporized electrode material until substantially current zero, the switch comprising: means defining a vacuum space having a pressure at least as low asv l0 mm. of mercury; a pair of electrodes symmetrical about a common axis and located in said space in opposed relation to define facing arcing surfaces, said electrodes being movable aiong said axis between a contact-making engaging position and a spaced position establishing a circuit interrupting are there between, each electrode having a head portion and a stem portion, said head portion-having an axial bore therein and defining an annular contact face, a solenoid member operatively connecting said head and stem portions, a high permeability magnetic core located Within the confines of said solenoid member insulatingly connected to said stem portion and extending through the axial bore of said head portion to a position near the plane of said annular contact face, each of said solenoids spiraling in opposite sense to produce substantially identical opposed magnetic fields, said magnetic fields determined by said cores and being substantially parallel with the axis of said electrodes and fringing radially adjacent said annular contact faces, the arcing surfaces of said electrodes having substantially the same shape as the fiux lines of said magnetic field, said magnetic field so influencing the circuit interrupting arc established through the vaporized metal of the electrodes that said are forms with footpoints substantially normal to said magnetic field rotates about the axis of said electrodes and is maintained on said arcing surfaces until substantially current zero is reached, and

a plurality of annular plates located Within said vacuum space in surrounding spaced relationship to the head portions of said electrodes, said annular plates providing condensing surfaces for said vaporized metal.

4. An alternating current vacuum switch in which a circuit interrupting arc is maintained by vaporized electrode material until substantially current zero, the switch comprising: means defining a vacuum space having a pressure at least as low as 10- mm. of mercury; a pair of electrodes symmetrical about a common axis and located in said space in opposed relation to define facing arcing surfaces, the arcing surfaces of at least one of said electrodes being formed of a material selected from the group consisting of tin, antimony, lead, zinc, manganese, bismuth and alloys thereof, said electrodes being movable along said axis between a contact-making engaging position and a spaced position establishing a circuit interrupting arc therebetween, each electrode having a head portion and a stem portion, said head portion having an axial bore therein and defining an annular contact face, a solenoid member operatively connecting said head and stem portions, a high permeability magnetic core located within the confines of said solenoid member insulatingly connected to said stern portion and extending through the axial bore of said head portion to a position near the plane of said annular contact face, each of said solenoids spiraling in opposite sense to produce substantially identical opposed magnetic fields, said magnetic field determined by said cores and being substantially parallel with the axis of said electrodes and fringing radially adjacent said annular contact faces, the arcing surfaces of said electrodes having substantially the same shape as the flux lines of said magnetic field, said magnetic field so influencing the circuit interrupting arc established through the vaporized metal of the electrodes that said are forms with footpoints substantially normal to said magnetic field rotates about the axis of said electrodes and is maintained on said arcing surfaces until substantially current zero is reached.

References Cited in the file of this patent UNITED STATES PATENTS Re. 21,Q87 Rankin May 16, 1939 1,925,858 Baker Sept. 5, 1933 2,411,892 Peters Dec. 3, 1946 2,411,893 Peters Dec. 3, 1946 2,900,476 Reece Aug. 18, 1959 FOREIGN PATENTS 703,101 Great Britain Jan. 27, 1954 787,846 Great Britain Dec. 18, 1957 

